This invention relates generally to a system for applying a tensioning band to articles and particularly to such a system for applying an implosion protecting band to a cathode ray tube (CRT) with a tension between known limits.
In the operation of a CRT an electron beam travels the length of the tube from an electron gun to a phosphor screen to produce a visual output and accordingly such tubes must be evacuated. Atmospheric pressure, therefore, tends to collapse, or implode, the envelope, creating a potentially hazardous condition. The hazards of implosion can be substantially reduced or eliminated by applying a tension around the envelope in the area between the screen and the seam where the screen and funnel are joined. One common and successful method of implosion protecting a CRT consists of a tensioned metal band which is looped around the envelope at the stress area between the screen and the seam. A metal clip is slipped over the double layered band and the free end firmly held while the other end is pulled into a tension. After the proper tension is applied, such as 1500 pounds (675 kilograms), the clip and both layers of the metal band are crimped, the tensioning device is released and the untensioned free end of the band is cut loose. This technique of applying tension is successful in greatly reducing the hazards of envelope implosion. However, a problem frequently arises because the tension must be within a particular range. Too low a tension will be ineffective in reducing the hazards of implosion and too high a tension will add excessive strain to the envelope, thereby creating a different hazard. Therefore, there is a need for a system which applies the tensioning band with a tension falling within a prescribed range. The instant invention is directed to a system which meets these capabilities.
The tool disclosed in application Ser. No. 200,538 filed of even data herewith by Laurence B. Kimbrough and entitled "HOLDING AND NOTCHING TOOL FOR CRT IMPLOSION PROTECTION" can be used in an embodiment made in accordance with the instant invention.